Process of electrolytic deburring of metal



United States Patent 2,730,494 PROCESS OF ELECTROLYTIC DEBURRING OF METAL Milton H. Bennett, Detroit, Micl1., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware No Drawing. Application September 16, 1950, Serial No. 185,317

7 Claims. (Cl. 204-145) This invention has to do with electrolytically deburring or smoothing metal.

The process of the present invention is especially adapted to remove burrs, machining marks and other roughnesses whether natural or caused from manufacturing processes, from metal objects that have been stamped, machined, heat treated or subjected to other processes that corrode or roughen the surface of the object.

The primary object of the invention is the provision of a relatively inexpensive and rapid process for smoothing or deburring metal parts. It is especially adapted to remove burrs from complex shaped parts where mechanical removal is diflicult.

The process consists essentially of the anodic treatment of the work to be smoothed or deburred in two separate solutions. The first is a solution of hydrochloric acid and water while the second solution is one consisting of hydrochloric acid, phosphoric acid and water or phosphoric acid and water. By means of the anodic treatment in the first solution the burrs or roughness is removed rapidly. However, this operation leaves a black smudge on the work which is removed by anodic treatment in the second solution.

A preferred deburring or solution Number 1 consists of 10% by volume of commercially concentrated hydrochloric acid (specific gravity 1.19) and 90% water by volume. The anodic treatment in solution No. 1 may be carried out at any temperature from about 60% F. up to about 160 F. For practical reasons it is preferred to carry out the treatment at about normal room temperature of about 70 F. While the optimum solution employed for the first treatment consists of a solution of 10% by volume of commercially concentrated hydrochloric acid and 90% by volume of water, the concentration of the hydrochloric acid may be varied anywhere Within the approximate limits of 2 to 60% by volume.

In most instances the concentrations of hydrochloric acid range between and 30% The current density in any specific instance is not sharply'critical and considerable variation is permissible. It will vary with the ship of the anode and cathode. Preferably shaped cathodes are used to concentrate the current in recessed areas. For best results the cathode area should greatly exceed the anode area, for example, on the order of five to one or in some cases may be as high as ten to one. The anode to cathode spacing can be varied from about A3 to about 12" but /2" seems to be the most usable spacing in most applications. Where a close spacing is employed the solution should be agitated to prevent gas pockets which result in high current resistance.

When the parts being treated have roughnesses extending generally over the entire surface the entire part may be immersed in solution Number 1 and treated anodically therein until the roughnesses are removed. In many instances the parts have a burr along only one edge. In such cases only the burr and fringe areas need be immersed in solution Number 1 and anodically treated size of the work and the relation- 1.5 to 6 amperes per square inch of total surface area of the part in solution I S to 30 amperes per square inch of affected area (burr plus fringe area).

Five to twenty-four volts direct current are required to maintain the foregoing current flow.

Depending on acid concentration, spacing, current densities and size of burr the removal time may vary from approximately one minute to fifteen minutes. Typi: cal burrs on low carbon sheet steel parts have been re: moved in from three to six minutes.

A preferred solution Number 2 employed to remove anodically a light black smut or smudge which appears on the work after anodic treatment in solution No. 1 is one consisting of 61% by volume of commercially concentrated phosphoric acid solutionH3P04), 13% by volume commercially concentrated hydrochloric acid (specific gravity 1.19) and 26% by volume of water. This solution gives good results at normal room temperature. However, suitable results are also obtained when temperatures varying from about 60 F. up to about 160 F. are employed. The voltage, current, spacing and other conditions are substantially the same as those employed for solution No. 1. In general, a time of about 40 to 60 seconds is required in order to remove the smudge. The solution just described appears to be the optimum one for removing the smudge. However, rather wide variations in the proportions of the hydrochloric acid, phosphoric acid and water are permissible. For example, solutions consisting of 20 to parts by volume of commercially concentrated phosphoric acid, 5 to 20 parts by volume of Water and 2 to 10 parts by volume of commercially concentrated hydrochloric acid (specific gravity 1.19) may be employed. Another solution which may be used in the anodic treatment for removal of the smudge is one consisting of phosphoric acid and water. In this example the proportions of phosphoric acid and water also may vary widely. For instance solutions consisting of about 20 to 95 parts by volume commercially concentrated phosphoric acid (85% solution) and 5 to 20 parts by volume water may be employed.

Various changes and modifications of the embodiments of my invention described herein may be made by those skilled in the art without departing from the principles and spirit of the invention.

I claim:

1. The method of removing a burr from a ferrous'metal member containing carbon and forming a clean, bright surface thereon which comprises immersing at least'the portion of the member having the burr thereon in a first solution consisting of approximately 2 to 60 per cent by volume of commercially concentrated hydrochloric acid (specific gravity 1.19) and the balance water, passing direct current through said first solution with the member as anode until the burr has been removed, and a dark smudge left on the member, thereafter placing at least that portion of the member having the dark smudge thereon in a second solution of the class consisting of (a) 20 to 95 parts by volume of commercially concentrated phosphoric acid (85% acid), 2 to 10 parts by volume of commercially concentrated hydrochloric acid (specific gravity 1.19) and 5 to 20 parts of water and (b) 20 to 95 parts by volume of commercially concentrated phosphoric acid (85% acid) and 5 to 20 parts by volume of water, and passing direct current through the second solution with the member as anode until the dark smudge resulting from treatment in the first solution is removed.

ber in a second solution of the class-of solutions con- Sistiqg of.(a) 20-.to 95 parts by vvolume of commercially concentrated phosphoric acid (85%), 2 to parts by volume of commercially concentrated hydrochloric acid (specific gravity1.I9) and 5 to parts of water and (b) 20 to 95 parts by volume of commercially concentrated phosphoric acid (85 and "5 to 20parts by volume of water, and passing direct current through the second solutionwith the member as anode until the dark smudge resulting from treatment in the first solution is removed.

3. The method of removing a burr from a steel memher and forming a clean, bright surface thereon which comprises immersing at leastthe portion of the member having the burr thereon in a first solution consisting of approximatelyZ to percent by volume of commercially concentrated hydrochloric acid (specific gravity 1.19)

and thebalance water, passing direct current through said first solution with the member as anode until the burr hasfbeen removed and a dark smudge left on the member,jthereafter placing the member in a second solution consisting of.20 to 95 parts by volume of commercially concentrated phosphoric acid 5 to 20 parts by volume or water, and 2 to 10 parts by volume of commercially concentrated hydrochloric acid (specific gravity 1219) and passing direct current through said second solution with the memberas anode until the dark smudge 5 resulting from treatment in the first solution has been removed.

4;"Ifhc method of removing a burr from a steel member and forming a clean, bright surface thereon which comprises immersing atleast the portion of the member having the burr thereon in a first solution consisting of approximately'Z to '60 percent by volume of commercially concentrated hydrochloric acid (specific gravity 1.19) and thebalance water, passing direct current through said solution with the member as anode until the burr has beenremoved and a dark .smudge left on the member, thereafter placing the member in a second solution consisting of 61% by volume phosphoric acid, 26% by volume water and 13% by volume commercially concentrated hydrochloric acid (specific gravity 1.19) and passing direct current through said second solution with the member as anode untilthe dark smudge resulting from treatment in the first solution has been removed.

5. The method of removing a burr from a steel memher and forming a clean, bright surface thereon which comprises immersing .at' least the portion of the member ha'ving-theburr-thereon in a'first solution consisting of 'aboutI'0% by volume of commercially concentratedhydrochloric acid (specific gravity 1.19) and about by volume of water, passing direct current through said solution-with the member-asanode until the-burr is re: moved and a smudge left on the member, thereafter inimersing that portion of the member having the smudge thereon in a second solution consisting of about 61% by volume commercially concentrated phosphoric acid (85%), 26% by volume water and 13% by volume commercially concentrated hydrochloric acid (specific gravity 1.19) and passing direct current through said second solution with said'member as anode until said smudge is removed.

6. The method of removing a burr from a sheet steel member and forming a clean, bright surface thereon which comprises immersing at least the portion of the member having the burr thereon in a first solution consisting of about 10% by volume of commercially concentrated hydrochloric acid (specific gravity 1.19) and about 90% by volume of Water, passing direct current through said solution with the member as anode until the burr is removed and a smudge left on the member, thereafter immersing that portion of the member having the smudge thereon in a second solution consisting of about 61% by volume commercially concentrated phosphoric acid (85% H3904), 26% by volume water and 13% by volume commercially concentrated hydrochloric acid (specific gravity 1.19) and pas-sing direct current through said second solution with said member as anode until said smudge is removed, said solutions being at a temperature within the approximate range of 60 to F.

7. The method of removing a burr from a sheet steel member and forming a clean, bright surface thereon which comprises immersing at least the portion of the member having the burr thereon in a first solution consisting of about 10% by volume of commercially concentrated hydrochloric acid (specific gravity 1.19) and about 90% by volume of water, passing direct current through said solution with the member as anode until the burr is removed and a smudge left on the member, thereafter immersing that portion of the member having the smudge thereon in a second solution consisting of about 61% by volume commercially concentrated phosphoric acid (85% Ha'POq), 26% by volume water and 13% by volume commercially concentrated hydrochloric acid (specific gravity 1.19) and passing direct current through said second solution with said member as anode until said smudge is removed, said solutions being at a temperature of approximately 70 F.

References Cited in the file of this patent UNITED STATES PATENTS 1,658,222 Burns etal. Feb. 7, 1928 1,916,503 Wilson July 4, 1933 2,382,549 Edmonson Aug. 14, 1945 2,559,445 Lotz July 3, 1951 FOREIGN PATENTS 27,099 Great Britain of 1906 489,884 Great Britain Aug. 5, 1938 

1. THE METHOD OF REMOVING A BURR FROM A FERROUS METAL MEMBER CONTAINING CARBON AND FORMING A CLEAN, BRIGHT SURFACE THEREON WHICH COMPRISES IMMERSING AT LEAST THE PORTION OF THE MEMBER HAVING THE BURR THEREON IN A FIRST SOLUTION CONSISTING OF APPROXIMATELY 2 TO 60 PER CENT BY VOLUME OF COMMERICALLY CONCENTRATED HYDROCHLORIC ACID (SPECIFIC GRAVITY 1.19) AND THE BALANCE WATER, PASSING DIRECT CURRENT THROUGH SAID FIRST SOLUTION WITH THE MEMBER AS ANODE UNTIL THE BURR HAS BEEN REMOVED, AND A DARK SMUDGE LEFT ON THE MEMBER, THEREAFTER PLACING AT LEAST THAT PORTION OF THE MEMBER HAVING THE DARK SMUDGE THEREON IN A SECOND SOLUTION OF THE CLASS CONSISTING OF (A) 20 TO 95 PARTS BY VOLUME OF COMMERICALLY CONCENTRATED PHOSPHORIC ACID (85% ACID), 2 TO 10 PARTS BY VOLUME OF COMMERCIALLY CONCENTRATED HYDROCHLORIC ACID (SPECIFIC GRAVITY 1.19) AND 5 TO 20 PARTS OF WATER AND (B) 20 TO 95 PARTS BY VOLUME OF COMMERCIALLY OCNCENTRATED PHOSPHORIC ACID (85% ACID) AND 5 TO 20 PARTS BY VOLUME OF WATER, AND PASSING DIRECT CURRENT THROUGH THE SECOND SOLUTION WITH THE MEMBER AS ANODE UNTIL THE DARK SMUDGE RESULTING FROM TREATMENT IN THE FIRST SOLUTION IS REMOVED. 